Surgical threads or sutures have long been known in the art, and the medical profession has become accustomed to using gut or monofilament threads or sutures for sewing incisions or wounds. Such gut or monofilament threads have been well adapted to medical use, but have always had the disadvantage of being difficult to tie in a secure knot. This is the result of the bending stiffness to the gut or monofilament, but the very characteristic which makes it effective for threading through the eye of a surgical needle causes it to resist loop formation, and this relative stiffness in flexure contributes to the difficulty of forming a secure knot.
It has been well known in the textile art that braiding is an excellent means of converting several continuous filaments or yarns into a coherent linear yarn-like structure which translates, most efficiently, the strength potential of the constituents into the total strengths of the yarn-like structure.
Between the monofilaments and gut at one end of the spectrum, and braiding at the other end, there are a variety of twisted yarns, either single or multi-ply, which can be used to form a suture, but such twisted yarn, of comparable strength and coherence to the braided yarn, would be relatively stiff in flexure and would, like the monofilaments and gut, resist loop formation during knotting. Of these materials, the braided structures are usually tubular and are constructed so that the tightness of the braid can be controlled during formation.
Thus, though a braided structure would provide an excellent suture from the standpoint of tying a secure surgical knot, its inherent lack of stiffness prevents it from easy threading through a surgical needle, or for passing through the flesh.
Prior inventors have approached this problem in a number of different ways, and of relevance is the structure shown in Myers U.S. Pat. No. 3,212,502, wherein a monofilament is introduced into a tube, the tube fastened to a needle, and the tube plus needle used to draw the monofilament through the wound, whereafter the tube is removed and the monofilament left behind to do the tying.
The combination of a braided yarn and a monofilament for use in a surgical suture is also shown in Pearson U.S. Pat. No. 3,130,278, but in this case the braided portion and the monofilament are arranged in end-to-end relationship so that the braided portion is used to draw the monofilament into the flesh.
More recently, the Shalaby U.S. Pat. No. 4,105,034 discloses a structure wherein either braided or monofilament surgical sutures have tying characteristics improved by coating with certain chemicals.